Injection system



W. T. SWEENEY 2 SheetsShet 1 Filed July 3, 1968 Oct-20,1970 w.1'.SWEENEY 3,53 ,945 f INJECTION SYSTEM Filed July 5, 1968 z Sheets-Sheet 2United States Patent 3,534,945 INJECTION SYSTEM William T. Sweeney,Cochituate, Mass., assignor t0 Vacumetrics, Inc., Waltham, Mass., acorporation of Massachusetts Filed July 3, 1968, Ser. No. 742,277

Int. Cl. F27b 1/20 US. Cl. 263-1 8 Claims ABSTRACT OF THE DISCLOSURESmall amounts of material are introduced into a vacuum-tight enclosureby an enjection system which makes use of a series of slugs, some ofwhich have cavities for receipt of the material to be introduced intothe enclosure, and others of which are solid. The slugs are introducedinto the enclosure in series through a channel which is just wide enoughto permit the slugs to move through it, but which is narrow enough sothat pressure between the outer surfaces of the slugs and the innersurface of the channel maintains a vacuum-tight seal. Each cavitied slugcontaining material to be introduced is flanked by solid slugs in orderto preserve the vacuum-tight property of the enclosure.

BACKGROUND OF THE INVENTION Field of the invention The invention relatesto vacuum-tight systems, and in particular to an injection mechanism forintroducing material into a vacuum-tight enclosure, such as theevacuated region associated with a mass spectrometer. However, theinvention is not limited to injection into an evacuated region, butincludes injection into a pressurized region or indeed injection into anenclosure at atmospheric pressure.

BACKGROUND OF THE INVENTION Description of the prior art Many analyticaland research instruments used to study organic materials required thesample to be in the vapor phase. Such instruments may operate under lowor high static pressures or under flow conditions. Whatever theoperating conditions, the introduction of the sample itself should notsignificantly disturb the operation of the in strument. For example, amass spectrometer commonly operates at 10 mm. Hg pressure. Thus duringsample introduction the system must not be exposed to atmosphericpressure, for the resultant pre'ssure surge could cause significantdamage.

In cases where the sample is naturally in the liquid phase, an inletsystem commonly used for a mass spectrometer includes a bulb connectedby one line to a vacuum pump and by another line to the ion source ofthe mass spectrometer. Vapor flow through each line is controlled bymeans of a valve therein. By means of these valves, the bulb is sealedoff from the ion source, and evacuated by means of the vacuum pump.After evacuation of the bulb, the sample in liquid phase is introducedinto the evacuated bulb by means of a syringe passed through a rubbermembrane or septum connected in some manner to the bulb. The bulb isthen heated, so as to vaporize the liquid sample in the bulb. The valvein the line from the bulb to the ion source is then opened, in order topermit the sample to flow in vapor phase towards the ion source. In theline joining the bulb to the ion "Ice source some type of porous plug ordiaphragm with a small hole in it is used to allow the sample in vaporphase to leak at a known rate into the ion source.

This technique suifers from the disadvantage that heat and certainchemicals will decompose the septum or harden it, with the result thateither the syringe will not penetrate it or, upon removal, the septummaterial will not seal up the puncture, thereby causing an air leak.Further, all injected materials must be in the liquid state to behandled by the syringe. Thus a material which is a solid at roomtemperature must be dissolved in some solvent and then injected. Thesolvent may inhibit the performance of the instrument. Also, not allmaterials are soluble in the commonly available solvents.

In the above described arrangement, as in the case of the invention, thesample is introduced directly into the reservoir in nongaseous phase insuch a way as not to impair the vacuum, and the sample is vaporized inthe reservoir itself. The reservoir is needed in order to provide acontrolled supply of vaporous sample and therefore is rather closelyconnected to the ultimate region of use, such as the ion source of themass spectrometer, and in general is kept evacuated to about the samedegree of vacuum as that in the ultimate region of use.

An alternate system has been used in the prior art in the case of solidsamples. In this system, the sample is not introduced directly into thereservoir in the nongaseous phase; instead, the evaporation chamber isseparated from the reservoir and is sealed off therefrom by one or morevalves until the evaporated chamber has been evacuated and the samplesubsequently evaporated. The evaporation chamber may be relativelysmall, and the sample in solid phase is introduced into the evaporationchamber at atmospheric pressure, without any effort to preserve a vacuumtherein. The evaporation chamber is evacuated repeatedly for each newsample. Such a device is generally known as a hot-box. Both thereservoir and the small evaporation chamber are inside an oven whichprovides the heat necessary to evaporate the solid sample. One end of aglass neck is connected to the reservoir by means of a valve orstop-cock. At the other end of the glass neck there is a ground-glassjoint (either male or female), to which the small evaporation chamber isremovably attached after the solid sample has been introduced therein.The air is then pumped away from the evacuation chamber via a suitableconnection in the glass neck. After evacuation, the evacuation chamberand the reservoir are heated by means of the oven. When sufiiciently hotto generate a vapor pressure of the solid, the valve or stop-cock isopened to allow the vapor into the reservoir. Thus the solid sample isvaporized before it is introduced into the reservoir by providing asmall, readily removable evaporation chamber closely connected to thereservoir and heated in a common oven with the reservoir. The portion ofthe oven housing the small evaporation chamber may be a moveable sectionwhich swings out of the way in order to provide ready access to thesmall evaporation chamber.

This so-called hot-box technique is time consuming, has samplecontamination problems associated with it, presents difficulty inmaintaining the reservoir and small evaporation chamber at equaltemperatures while heated by the oven, and is more prone to breakagethan the system of the invention. As previously noted, in the system ofthe invention the solid itself is introduced into the reservoir beforeevaporation.

3 SUMMARY The slug injection system of the invention overcomes all theproblems of the prior art hereinabove referred to. In the particularembodiment of the invention described herein (but to which the inventionis not limited), namely, its use in connection with a mass spectrometer,the injection mechanism itself is utilized in conjunction with two othermain components, namely, an oven and glassware. The glassware includes aglass bulb, manifold, and valves. The injection system itself comprisesfour main units: (1) slugs; (2) block; (3) baseplate; and (4) injectionsleeve. Some of the slugs are solid, and some have cavities forreception of small amounts of material to be injected. All the slugs areadapted to slide through the injection sleeve snugly, and at least onesolid slug is in the injection sleeve at all times in order to renderthe injection sleeve vacuum-tight. The material to be injected isintroduced into the cavity of a cavitied slug, and that slug is thenintroduced into the glass bulb along with its cargo via the injectionsleeve, flanked by solid slugs in order to preserve vacuum-tightness atall times. Once in the glass bulb, the material may be vaporized bymeans of the oven, and the vapor transported to some other region, suchas the ion source of a mass spectrometer, via the manifold. The blockand base-plate cooperate to provide the mechanism for pushing the slugsthrough the injection sleeve.

BRIEF DESCRIPTION OF THE DRAWING The invention may best understood fromthe following detailed description thereof, having reference to theaccompanying drawings, in which:

FIG. 1 is a schematic diagram of an all-glass heated inlet systemincorporating one embodiment of the invention;

FIG. 2 is an isometric view of the injection system used in theapparatus of FIG. 1;

FIG. 3 is a longitudinal central section through the injection sleeve ofthe injection system of FIG. 2;

FIG. 4 is a detail of the view of FIG. 3 and shows a solid slug;

FIG. .5 is another detail of the injection sleeve of FIG. 3 and shows acavitied slug;

FIG. 6 is a view showing the base plate used in connection with theinjection sleeve of FIG. 3; and

FIG. 7 is a view similar to that of FIG. 3 and show ing a modificationof the embodiment shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, thefirst to FIG. 1 thereof, the total inlet system consists of three maincomponents: namely, the injection mechanism 1, an oven 2 and glassware.The glassware includes a glass bulb or reservoir 3, a manifold 4, andvalves 5, 6, 7 and 8. Although the system will be described as havingfour valves, it will be apparent from the ensuing description that thetotal inlet system will work with a minimum of three valves.

The oven 2 provides structural support for the injection mechanism 1 andthe glassware. It also provides a controlled temperature environment forvaporization of the sample.

The reservoir 3, within which the sample is vaporized by the heatgenerated by the oven 2, is connected by means of suitable tubing 9 andglass 10 to the injection mechanism 1. Samples to be vaporized areintroduced into the reservoir 3 by the injection mechanism 1 to bedescribed in detail hereinafter. At the bottom of the reservoir 3 thereis an O-ring connection 11, which when opened allows access to thecontents of the reservoir 3. The glass bulb reservoir 3 includes an arm12 which terminates in a glass valve attached to the manifold 4Additional glass valves 6, 7, 8 are attached to the manifold 4 and areconnected to external lines 13, 14, 15, respectively, each lineincluding a length of suitable tubing 16, 17, and 18. The external lines13, 14, 15 lead to a vacuum pump 19, an external inlet system 20, and anion source 21 of a mass spectrometer, respectively. In all cases thetubing 9, 16, 17, 18 preferabl consists of flexible, heatshrinkableTeflon tubing, Where Teflon is the trade name owned by E. I. du Pont deNemours and Co., Inc. for tetrafluoroethylene and fluorinatedethylpropylene resins. The use of shrinkable Teflon tubing as jointsaffords a cushion against both physical and thermal shock. In addition,the tubing may be easily cut so that parts may be removed or changesmade.

The valves 5, 6, 7, 8 may consist of a glass ball and socket joint inwhich the ball is connected to a glass rod containing a magnet. Thevalve is opened or closed by the action of an external magnet controlledmanually by the operator.

The operation of the device shown in FIG. 1 will now be describedstarting from the point in the cycle at which all valves are closed andthe bulb has been evacuated. A sample in liquid or solid phase isinjected into the reservoir 3 via the injection mechanism 1 of theinvention, and the heat from the oven 2 causes it to vaporize. The valve5 is then opened, allowing the vaporized sample to enter the manifold 4.Valve 8 is then opened, and the vaporized sample enters the ion source21 of the mass spectrometer. After conclusion of the experiment with themass spectrometer, the entire system may be evacuated by opening valve6. After evacuation, valve 5 which connects the reservoir 3 to themanifold 4, is closed and the reservoir 3 is then ready for injection ofanother sample. Valve 7 may be used to connect the manifold to any otherexternal inlet system 20 such as a gas inlet system.

The oven 2 may be heated by any of a number of conventional techniques.One such technique makes use of two strip heaters, shown at 36 in FIG.1, each of which comprises a bar which may be, for example, 8 incheslong with a cross section of 4-inch by 4-inch. Each bar 36 is aresistance heater, and the current thereto is supplied via leads 37which may pass through the bottom or sides of the oven 2. The stripheaters 36 are supported at the bottom section of the oven 2, and a heatshield 38 is supported above the strip heaters 36 in order to preventhot spots and thus protect the reservoir 3. The leads 37 are connectedto an external controller 39 which varies the current so as to controlthe temperature within the oven 2.

The apparatus shown in FIG. 1 has been described in order to illustrateone possible use for the injection mechanism of the invention. However,it is clearly to be understood that the injection mechanism of theinvention is not limited in its usefulness to operation with a massspectrometer, but will be useful whenever it is desired to transferliquid or solid samples into an enclosed region, particularly fromanother region at a pressure different from that existing within theenclosed region.

The injection mechanism of the invention is shown in FIGS. 2 and 3.Referring thereto, the injection mechanism 1 essentially includes aninjection sleeve 21 through which a sequence of slugs 22, 23 is forcedby means of a suitable mechanical contrivance such as the rack andpinion gear mechanism shown in FIG. 2. This mechanism 24 is supported ona block 25 which in turn slides on a base plate 26 so as to move therack and pinion gear mechanism 24 into or out of alignment with theinjection sleeve 21.

The slugs are of two different types, solid and cavitied. A solid slug22 is shown in FIG. 4 and preferably comprises a solid gas free Tefloncylinder. A representative dimension is 0.250 inch long (plus .025 inch,minus .000 inch) and 0.188 inch in diameter (plus or minus .002 inch). Acavitied slug 23 is shown in FIG. 5; it also preferably comprises a(cavitied) gas free Teflon cylinder and has the same external dimensionsas the solid slug 22 but contains a cavity 27. For the dimensions of thesolid slug previously described, a representative cavity dimension wouldbe .098 inch in diameter (plus or minus .002 inch) and .188 inch deep.The cavitied slug 23 is used to hold the sample. One reason that Teflonis a preferred material for the slugs is that it will flow a very smallamount under pressure. Thus if there are any scratches on the surface ofthe injection sleeve, the slugs will plug them up.

Referring now to FIG. 3, the injection sleeve 21 is supported on thebase plate 26 and is aligned to engage the glass line 2-8 to thereservoir 3. The sleeve 21 screws into the bottom of the base plate 26which is fixed to the top of the oven 2. A cavitied slug 23 containingthe sample is inserted into the glass reservoir through the injectionsleeve 21. However, during intervals between injections, the injectionsleeve 21 has a solid slug 22 in the tapered neck 29. This neck 29 isshaped so that no slug will pass freely through it. However, each slugwill compress enough so that forced into the bottom portion of the neck29 it will provide a vacuum or pressure tight seal. Thus during theintervals between injections a solid slug provides this seal.

The base plate 26 provides a platform for the block 25 to slide upon.Referring now to FIG. 6, the base plate 26 contains two poppets 30, 31which provide forward and backward stops for the block motion. When theblock 25 is pushed to the back of the base plate 26 to stop 30, theupper portion of the injection sleeve 21 is revealed. It will berecalled that a solid slug 22 is already in position within the sleeve21. A cavitied slug 23 containing the sample is now placed in the sleeve21, followed by another solid slug 22. The block 25 is then pulledforward to stop 31.

At this position, the device is now in position to force the sample intothe reservoir 3. The block 25 contains a rack and pinion gear 24operated by a lever 32. When the lever 32 is pulled forward, the plunger33 on the end of the rack 34 moves down. This plunger 33 contacts theupper surface of the top solid slug 22 and forces all three slugsthrough the injection sleeve 21. The solid slug originally in the sleeve21 drops through into the reservoir 3 followed by the cavitied slugcontaining the sample.

The plunger 33 can only travel a certain distance, such as /2 inch, atwhich point the shoulder 35 on the plunger 33 bottoms on the base plate26. At this point the final solid slug is then in the proper position toprovide a vacuum seal and to allow another two slugs, first a cavitiedslug 23 and then a solid slug 22, to be loaded into the sleeve 21 aboveit. The whole operation takes less than a minute to accomplish and atall times a vacuum tight seal is provided as the slugs pass sequentiallythrough the injection sleeve. Only minute amounts of air trapped betweenthe slugs and the unfilled portion of the cavity in the cavitied slug 23are allowed to enter the system. Further, the slugs are preferably madeof a material such as Teflon which is chemically inert and heatresistant up to 800 F. and will not outgas in a vacuum.

'When sufficient slugs have accumulated in the bulb 3, they may beremoved by venting the system to the atmosphere and removing theconnection 11 at the bottom of the reservoir 3. The slugs will then dropthrough.

More bulky items may be inserted into the reservoir 3 by utilizing apair of cavitied slugs together with glass capillary tubing. Such anarrangement is shown in FIG. 7. Assuming the previously given dimensionsof the cavitied slug, such glass capillary-tubing should not havedimensions in excess of 0.376 inch long and .098 inch in diameter. Thesystem should be prepared so that the vacuum seal is provided by thecavitied slug with the cavity facing outward rather than with a solidslug. Then a sample, for example one taken from a liquid chromatographyunit contained in suitable glass capillary tubing 40, is inserted intothe cavity 41 in one cavitied slug 42 and capped with a second cavitiedslug 43 with opposite orientation. The slug pair 42, 43 enclosing thecapillary tubing 40 is then injected in a manner similar to the manneremployed to inject the cavitied slug 23 of FIG. 3, forcing the existingslug 44 ahead of it into the reser voir 3. As before, last to beinserted may be a solid slug, as shown at 45 in FIG. 7, or indeedanother cavitied slug with the cavity facing outward. In this way theglass tube 40, or any other type sample of this nature, may be inserted.Obviously, the size and shape of the sample is limited only bydimensions of the slug and the injection sleeve.

Having thus described the principles of the invention together withillustrative embodiments thereof, it is clearly to be understood thatalthough specific terms are employed they are used in a generic ordescriptive sense and not for purposes of limitation, the scope of theinvention being set forth in the following claims.

I claim:

1. Injection system comprising, in combination, an injection sleevehaving a minimum internal diameter, a multiplicity of cavitied slugshaving a maximum external diameter not less than that necessary toprovide a vacuum-tight seal during passage through said injectionsleeve, a multiplicity of solid slugs having a maximum external diameternot less than that necessary to provide a vacuum-tight seal duringpassage through said injection sleeve, and mechanical means forovercoming frictional forces between said maximum external diameters andsaid mnimum internal diameter and thereby forcing said slugs throughsaid injection sleeve.

2. Injection system for introducing small amounts of material into avacuum-tight enclosure, comprising, in combination, a vacuum-tightenclosure, an injection sleeve supported on said vacuum-tight enclosureand having a channel providing communication between the interior andthe exterior of said vacuum-tight enclosure, a multiplicity of solidslugs adapted to fit snugly in said channel, a multiplicity of cavitiedslugs adapted to fit snugly in said channel, and mechanical means forforcing said slugs through said channel.

3. A method of injecting small amounts of material into a region, whichmethod comprises introducing small amounts of such material into thecavity of a cavitied slug, flanking said slug with solid slugs, andmechanically forcing said slugs into said region through an injectionsleeve into which said slugs fit snugly.

4. System for introducing material in the gas phase into a region, saidsystem comprising in combination an evaporation reservoir, means forheating said reservoir, a vacuum pump, a manifold interconnecting saidreser voir, pump and evacuated region, valves adapted to shut off saidinterconnections, and an injection system for introducing small amountsof said material in a nongaseous phase into said reservoir, saidinjection system comprising, in combination with said reservoir, aninjection sleeve supported on said evaporation reservoir and having achannel providing communication between the interior and the exterior ofsaid reservoir, a multiplicity of solid slugs adapted to fit snugly insaid channel, a multiplicity of cavitied slugs adapted to fit snugly insaid channel, and mechanical means for forcing said slugs through saidchannel.

5. Injection system in accordance with claim 2, wherein said mechanicalmeans includes a plunger having a shoulder adapted to abut the externalextremity of said channel so as to limit the inward motion of theplunger and thus prevent the plunger from forcing the final slug throughthe channel.

6. Injection system in accordance with claim 2, wherein said mechanicalmeans includes a rack and pinion gear mechanism.

7. Injection system in accordance with claim 1, wherein said slugscomprise tetrafiuoroethylene and fluorinated ethylpropylene resins.

8. A method of injecting small amounts of material into an evacuatedregion sealed by an interinjection seal slug, which method comprisesintroducing small amounts References (Iited of such material into acapillary tube to be held between UNITED STATES PATENTS and within theopposed cavities of a pair of cavitied slugs,

and mechanically forcing said slugs into said evacuated 3176128 3/1965Ehrhardt et region through an injection sleeve into which said slugs fitsnugly, thereby ejecting said interinjection seal slug, the capillary,and the foremost cavitied slug, While leaving the hindmost cavitied slugas a replacement interinjection seal slug. 25 041 .9

5 JOHN J. CAMBY, Primary Examiner US. Cl. X.R.

